|Browse Projects > Detailed View
Develop Guidelines for the Design and Construction of Ultra-Thin Asphalt Concrete Overlays
Ultra-thin asphalt concrete (AC) overlays are defined as having a thickness of 1 inch or less which are to be used as the final wearing surface. In addition to the economic benefit of ultra-thin overlays there are many instances where the use of very thin overlays is desirable. Often geometric concerns, bridge clearances, curb and gutter situations mandate that only thin overlays are possible. A research study is required to provide a concise guide to designing and constructing these overlays.
A study is required to provide guidelines on the design and
construction of ultra-thin AC overlays.
It is critical to summarize the existing design methodologies, material
quality requirements, construction and performance information. It is necessary to develop concise
evaluation, design and construction guidelines for DOT's wishing to evaluate
the use of these materials. These recommendations must include minimum
aggregate quality requirements. It is
intended that these mixes should also be designed by DOT's using available
equipment (SUPERPAVE™) with possible additional performance tests. The performance tests will as a minimum
evaluate both rut and reflection cracking resistance. It is also critical to include the condition
of the existing pavement in establishing the desirable engineering properties
of the ultra-thin overlay.
With the escalating cost of asphalt materials it is critical that
cost effective solutions be developed for the maintenance of existing highway
networks. It is anticipated that the
ultra-thin mixes will be 20 to 30% more expensive than traditional materials,
but if the can be placed in 1 inch, as opposed to traditional 2 inch lift, the
economic payoff's are clear.
These mixes are already being used in several DOT around the US. However the performance of these mixes has
not been documented. The lessons learned need also to be documented. There is an urgent need to accelerate
nationwide implementation of ultra-thin overlays.
Several DOT's have developed specifications for very thin
overlays. The Ohio DOT has used its
"smoothseal" mix since the mid-1990's. These mixes are reported to be rut resistant
and maintain excellent skid properties.
Other DOT's such as Arizona, Maryland and Michigan
also have specifications for ultra-thin overlays. The National Center
for Asphalt Technology has been researching "screenings mixes" which
have been shown to have excellent rut resistance. The Texas DOT has developed and field tested
a Crack Attenuating Mix which is being specifically designed to pass both a
rutting and cracking requirements, initial performance results have been
promising. Other DOT's have also been active in this area but no systematic
evaluation has been made of overlay performance.
This project will be divided into 2 phases. In Phase 1 the researchers will:
Summarize existing DOT practices and performance. This will include visits to at least 4 States
which have placed Ultra-thin overlays.
As a minimum the performance will as a minimum include rutting,
reflection cracking and skid performance.
Use the information collected to develop guidelines on:
How to select candidate projects (including
structural evaluation and recommendations on when ultra thin overlays are not
How to design these mixes based on existing
pavement condition, pavement type and environment
recommendations (QC/QA recommendations)
In Phase 2 the research agency will be required to work with 3
DOT's. Each state DOT nominates two
pavements for consideration as candidates to receive an ultra-thin
overlay. The researchers will conduct a
structural evaluation of both and then to design ultra thin HMA mixes based on
their locally available aggregates. The
results from the evaluation and mix design will be presented to DOT engineers.
All the findings from Phases 1 and 2 will be included in the
studies final report.
|Sponsoring Committee:||AKP30, Design and Rehabilitation of Asphalt Pavements
|Research Period:||24 - 36 months|
|RNS Developer:||Trenton Clark|
|Index Terms:||Asphalt concrete pavements, Overlays (Pavements), Pavement design, Guidelines, Ultra-thin, Thickness, Economic benefits, |
Please click here if you wish to share
information or are aware of any research underway that addresses
issues in this research needs statement. The information may be
helpful to the sponsoring committee in keeping the statement